JP2010138350A - Method for producing non-aqueous pigment dispersion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a non-aqueous pigment dispersion excellent in preservation stability, and a coloring composition for color filters containing the non-aqueous pigment dispersion. <P>SOLUTION: (1) The method for producing a non-aqueous pigment dispersion is to prepare a pigment dispersion by mixing a pigment, organic solvent and water insoluble polymer dispersant, add a 1-5C alcohol to the dispersion, subsequently treat the dispersion by filtration to remove the water insoluble polymer dispersant and (2) the coloring composition for color filters contains the non-aqueous pigment dispersion prepared by the method. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a non-aqueous pigment dispersion and a coloring composition for a color filter containing the non-aqueous pigment dispersion.

Generally, if the pigment can be dispersed as fine and stable particles, the scattering to visible light will be reduced, so that it can be further utilized in a wide range of information materials such as paints, inks, cosmetics, and color filters. .
As a method for dispersing a pigment, a method is known in which particles are pulverized and pulverized using a media mill disperser by a shearing force / friction force by stirring and mixing, an impact force between media, and the like.
In the pigment dispersion step, an excessive amount of a polymer dispersant is usually used in order to smoothly perform the dispersion treatment. A part of the used polymer dispersant is adsorbed on the pigment, but the rest is present in an unadsorbed state on the pigment.
On the other hand, as the pigment is refined, the polymer dispersion agent used excessively becomes more susceptible to interactions such as interparticle cross-linking, resulting in an increase in viscosity resulting in stabilization of the dispersion state. It becomes difficult. Therefore, in order to maintain and ensure the stability of the pigment dispersion, it is preferable to reduce or remove excess polymer dispersant that may cause thickening or the like from the pigment dispersion.

For the purpose of improving the dispersion stability of pigments and the like, Patent Document 1 describes coloring after forming colored fine particles composed of a colorant and a polymer, followed by ultrafiltration or microfiltration, followed by adsorption treatment with an adsorbent and purification. A method for producing an aqueous dispersion of fine particles is disclosed. Patent Document 2 discloses a method in which colored fine particles containing an organic solvent are emulsified and dispersed in an aqueous medium using an ionic surfactant, and the organic solvent is removed. A method for purifying a colored fine particle dispersion that is purified by an adsorbent treatment and / or an ultrafiltration membrane treatment is disclosed.
Patent Document 3 discloses a dispersion liquid that is dry pulverized and has a maximum particle size of 20 μm or less and has a solubility of 1% or less in a solvent having a concentration of the pigment of 40% by mass or less. A method for purifying a pigment by filtration using an outer filtration membrane or a microfiltration membrane is disclosed.
However, Patent Documents 1 to 3 relate to ink jet recording inks, and are different from the technology related to non-aqueous pigment dispersions. Further, there is no disclosure of adding an alcohol to remove the polymer dispersant adsorbed on the pigment.

JP 2003-277672 A JP-A-2005-23116 JP 2003-342493 A

  An object of the present invention is to provide a method for producing a non-aqueous pigment dispersion excellent in storage stability and a coloring composition for a color filter containing the obtained non-aqueous pigment dispersion.

That is, the present invention provides the following (1) and (2).
(1) A water-insoluble polymer dispersant is prepared by adding a C1-5 alcohol to a pigment dispersion obtained by mixing a pigment, an organic solvent, and a water-insoluble polymer dispersant, followed by filtration. The manufacturing method of the non-aqueous pigment dispersion which removes.
(2) A coloring composition for a color filter containing the non-aqueous pigment dispersion obtained by the method (1).

  ADVANTAGE OF THE INVENTION According to this invention, the coloring composition for color filters containing the efficient manufacturing method of the non-aqueous pigment dispersion excellent in storage stability and the obtained non-aqueous pigment dispersion can be provided.

  The method for producing a non-aqueous pigment dispersion of the present invention comprises adding a C1-C5 alcohol to a pigment dispersion obtained by mixing a pigment, an organic solvent, and a water-insoluble polymer dispersant, followed by filtration treatment. Thus, the water-insoluble polymer dispersant is removed. Hereinafter, each component used in the present invention will be described.

<Pigment>
As the pigment used in the present invention, both inorganic pigments and organic pigments can be used. If necessary, they can be used in combination with extender pigments.
The hue is not particularly limited, and chromatic pigments such as red, yellow, blue, orange, green, violet, and white pigments can be used.
Examples of the inorganic pigment include carbon black, metal oxide, metal sulfide, and metal chloride. As the inorganic black pigment, carbon black is preferable, and examples thereof include furnace black, thermal lamp black, acetylene black, and channel black.
Examples of extender pigments include silica, calcium carbonate, and talc.

Examples of the organic pigment include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthraquinone pigments, and quinophthalone pigments.
Examples of red organic pigments include azo pigments, diazo pigments, condensed azo pigments, azo lake pigments, quinacridone pigments, perylene pigments, anthraquinone pigments, diketopyrrolopyrrole pigments, and the like.
More specifically, compounds classified as Pigment in the Color Index (published by The Society of Dyersand Colorists, 1997 edition) can be mentioned. For example, CI Pigment Yellow 12, 13, 13, 17, 20, 24, 31, 55, 74, 83, 93, 97, 109, 110, 120, 128, 137, 139, 151, 151, 153, 154, 155, 166, 168, 173, 174, 180, C.I.Pigment Orange 36, 43, 51, 71, 73; CI Pigment Red 9, 48, 57: 1, 97, 122, 123, 146, 149, 176, 177, 180, 184 185, 188, 202, 215, 254, 255, 264, 270, 272; CI Pigment Violet 19, 23, 29; CI Pigment Blue 15, 15: 1, 15: 2, 15: 3, 15: 4, 16, and 60; CI Pigment Green 7 and 36; CI Pigment Brown 23 and 25; CI Pigment Black 1 and 7 It is done.
Among these, diketopyrrolopyrrole pigments such as CI Pigment Red 254 and 255 are particularly preferred from the viewpoint of more effectively expressing the effects of the present invention. .

(Wherein, X ¹ and X ² each independently represent a hydrogen atom or a halogen atom, and Y ¹ and Y ² each independently represent a hydrogen atom or a —SO ₃ H group.)
Examples of the halogen atom of X ¹ and X ² in the general formula (1) include a fluorine atom and a chlorine atom.
There is no restriction | limiting in particular in the manufacturing method of the diketopyrrolopyrrole pigment represented by General formula (1). For example, it is produced by reacting benzonitrile or halogenated benzonitrile with a halogenated acetate such as bromoacetate in the presence of a reducing agent such as zinc powder, or by further sulfonating the obtained compound. be able to.

From the viewpoint of improving the lightness Y value, it is desirable to use a finely-pulverized product having an average primary particle diameter of preferably 100 nm or less, more preferably 20 to 60 nm. The average primary particle diameter of the pigment can be obtained by directly measuring the size of the primary particles from an electron micrograph. Specifically, the minor axis diameter and major axis diameter of each primary particle are measured and the average is obtained as the particle diameter of the particle, and the volume of each particle is obtained for 100 or more particles. The volume average particle diameter is obtained by approximating a cube with one side as the average primary particle diameter.
Preferable examples of commercially available diketopyrrolopyrrole pigments include Ciba Specialty Chemicals, C.I. I. Pigment Red 254 (a compound in which X ¹ and X ² are chlorine atoms and Y ¹ and Y ² are hydrogen atoms in the above formula (1)), trade names “Irgaphor Red B-CF”, “Irgaphor Red BT-CF” , “Irgazin DPP Red BO”, “Irgazin DPP Red BL”, “Chromophthal DPP Red BP”, “Chromophthal DPP Red BOC”, and the like.
The above pigments can be used alone or in combination of two or more.
In addition, from the viewpoint of increasing the affinity with an organic solvent for the pigment surface and enhancing the dispersion stability, a pigment that has been previously surface-treated with a resin, a polymer, a pigment derivative, or the like may be used. It may be contained in the dispersion treatment.

<Organic solvent>
The organic solvent used in the present invention is not particularly limited as long as it is other than an alcohol having 1 to 5 carbon atoms, but particularly when used as an oil-based ink for a color filter, a high-boiling organic solvent having a boiling point of 100 ° C. or higher should be used. preferable. Examples of such a high boiling point organic solvent include the following (i) to (v).
(I) Ethylene glycol alkyl ethers (cellosolves): ethylene glycol monomethyl ether, ethylene glycol diethyl ether, ethylene glycol monoethyl ether, etc. (ii) Diethylene glycol alkyl ethers (carbitols): diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol (Iii) Alcohols: ethylene glycol, diethylene glycol, glycerin, etc. (iv) Alkanediyl glycol dialkyl ethers: propylene glycol monomethyl ether, propylene glycol dimethyl ether, etc. (v) Alkanediyl glycol monoalkyl ether acetates: ethylene glycol Monomethyl ether acetate , Ethylene glycol monoethyl ether acetate, ethylene glycol monomethyl ether propionate, ethylene glycol monoethyl ether propionate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monomethyl ether propionate, propylene glycol monoethyl Ether propionate, diethylene glycol monomethyl ether acetate, diethylene glycol monobutyl ether acetate, etc. Among the above organic solvents, from the viewpoint of solubility or dispersibility of the water-insoluble polymer dispersant and dispersibility of the pigment, (iv) alkanediyl glycol mono Alkyl ether acetates are preferred, and propylene glycol monomethyl ether acetate Doo (PGMEA, boiling point: 146 ° C.), and diethylene glycol monobutyl ether acetate (BCA, boiling point: 247 ° C.) is particularly preferred.
These organic solvents can be used alone or in combination of two or more.

<Water-insoluble polymer dispersant>
The water-insoluble polymer dispersant used in the present invention (hereinafter, also simply referred to as “polymer dispersant”) may be any one that can disperse a pigment in an organic solvent in a stable finely divided state. Water insoluble polymeric dispersants can be used. The water-insoluble polymer dispersant is considered to have a function as a binder when forming a color filter or the like.
Here, the water-insoluble polymer dispersant is a polymer that constitutes the polymer dispersant, dried at 105 ° C. for 2 hours, and then dissolved in 100 g of water at 25 ° C., so that the dissolved amount is 10 g or less, The polymer is preferably 5 g or less, more preferably 1 g or less. When the polymer has a salt-forming group, the dissolution amount is a dissolution amount when the salt-forming group of the polymer is neutralized 100% with acetic acid or sodium hydroxide depending on the type.
Examples of the polymer dispersant include an amide skeleton in the main chain described in JP-A-3-277673, JP-A-10-339949, JP-A-2003-517063, etc., and the side chain is methacrylic. Graft polymer comprising macromonomer by acid ester; polyester oligomer having aliphatic hydroxycarboxylic acid residue described in JP-B-7-96654, JP-A-7-207178, etc .; organosiloxane polymer (Shin-Etsu Chemical Co., Ltd.) (Meth) acrylic acid-based (co) polymer (manufactured by Kyoei Yushi Chemical Co., Ltd., Polyflow No. 75, 90, 95, etc.); Other commercially available products such as Solsperse manufactured by GENECA 3000, 5000, 9000, 12000, 13240, 13940, 17000, 2 000, 24000, 26000, 28000, etc., and various types of ALSPER PB-821, PB-822, PB-880 manufactured by Ajinomoto Fine Techno Co., Ltd. (composition (weight ratio): polyallylamine / polycaprolactone = 5/95, Mw: 8,000], Isonet S-20 manufactured by Sanyo Chemical Co., Ltd., DISPERBYK-161, DISPERBYK-2001 manufactured by Big Chemie Japan Co., Ltd., and the like.

In particular, a polymer composed of a structural unit containing at least a monomer having an adsorptive property to a pigment and a structural unit containing a monomer having an affinity for an organic solvent is preferable from the viewpoint of improving dispersion stability. These can be appropriately selected and used depending on the pigment and the organic solvent species.
For example, when the diketopyrrolopyrrole pigment is used as the pigment and the organic solvent is propylene glycol monomethyl ether acetate (PGMEA) or diethylene glycol monobutyl ether acetate (BCA), the main chain includes the following compounds from the viewpoint of improving the adsorptivity to the pigment. The structural unit (a) is preferably included, and from the viewpoint of improving the viscosity stability of the pigment dispersion, the main chain preferably includes the following structural unit (b), and the viewpoint of improving the affinity with the organic solvent. Therefore, it is preferable that the side chain contains the following structural unit (c).
Main chain: structural unit derived from a vinyl monomer containing a nitrogen atom (a) and structural unit derived from a vinyl monomer containing a hydroxyl group (b)
Side chain: Structural unit derived from alkyl (meth) acrylate macromer (c)
The structural units (a) to (c) can be appropriately selected according to various purposes.

[Structural unit (a)]
The vinyl monomer containing a nitrogen atom that forms the structural unit (a) contained in the main chain of the polymer dispersant is preferably a vinyl monomer having an amide bond, and more specifically, (meth) acrylamides Vinylpyrrolidones, vinylpyridines, nitrogen-containing styrene monomers, nitrogen-containing (meth) acrylic acid esters, and the like.
Among these, (meth) acrylamides and vinylpyrrolidones are preferable, and N-vinylpyrrolidone is particularly preferable from the viewpoint of adsorptivity to the pigment.

[Structural unit (b)]
Examples of the vinyl monomer containing a hydroxyl group that forms the structural unit (b) contained in the main chain of the polymer dispersant include compounds represented by the following general formula (2).
^{_{CH 2 = C (R 4)}} COO (R 5 O) n H (2)
(In the formula, R ⁴ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R ⁵ is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, and n is an average added mole number. And is a number from 1 to 60.)
In the formula (2), suitable examples of R ^4, a methyl group, an ethyl group, (iso) propyl group and the like, and as the hetero atom of R ^5, for example, nitrogen atom, oxygen atom, halogen atom and sulfur atom. preferred examples of R ⁵ O groups are oxyethylene groups, oxy oxytrimethylene, oxy-1,2-diyl group, oxytetramethylene group and the carbon consisting of two or more thereof The oxyalkanediyl group (oxyalkylene group) of several 2-7 is mentioned. n is preferably a number from 1 to 30.
Among these, from the viewpoint of viscosity stability of the pigment dispersion, 2-hydroxyethyl (meth) acrylate, polyethylene glycol monomethacrylate, and polypropylene glycol methacrylate are preferable, and 2-hydroxyethyl (meth) acrylate is particularly preferable.

[Structural unit (c)]
The alkyl (meth) acrylate-based macromer that forms the structural unit (c) contained in the side chain of the polymer dispersant has a structural unit derived from alkyl (meth) acrylate, and has a polymerizable functional group at one end thereof. It may have. The side chain containing the structural unit (c) derived from the alkyl (meth) acrylate macromer can be obtained by copolymerizing an alkyl (meth) acrylate macromer having a polymerizable functional group at one end, As for the structural unit (c), one or more structural units may be contained in the side chain. Specific examples thereof include a homopolymer of alkyl (meth) acrylate having a polymerizable functional group at one end, or a copolymer of an alkyl (meth) acrylate having a polymerizable functional group at one end and another monomer. Coalescence is mentioned.
In addition, as alkyl (meth) acrylate which forms the structural unit (c) derived from alkyl (meth) acrylate, Preferably it is C1-C8, More preferably, it is C1-C6, Most preferably, it is C1-C3. And those having a linear or branched alkyl group. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, (iso or tertiary) butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (Meth) acrylate etc. are mentioned. Among these, methyl (meth) acrylate, ethyl (meth) acrylate, and (iso) propyl (meth) acrylate are particularly preferable. These alkyl (meth) acrylates can be used individually by 1 type or in mixture of 2 or more types.
In the present specification, “(iso or tertiary)” and “(iso)” mean both the case where these groups are present and the case where these groups are not present, and these groups are not present. In the case, it indicates normal. “(Meth) acrylate” means both acrylate and methacrylate.

The polymerizable functional group of the alkyl (meth) acrylate macromer is preferably an acryloyloxy group or a methacryloyloxy group.
Examples of other monomers copolymerized with alkyl (meth) acrylate include styrene monomers such as styrene, α-methylstyrene, vinyltoluene, and benzyl (meth) acrylate. In the alkyl (meth) acrylate-based macromer, the content of the structural unit derived from the alkyl (meth) acrylate is preferably 80% by weight or more, more preferably 90% by weight or more, and particularly preferably substantially 100% by weight. “Substantially” means that it may contain constituent units derived from other monomers in the amount of impurities.
The number average molecular weight of the alkyl (meth) acrylate macromer is 800 to 4,000, preferably 1,000 to 3,500, more preferably 1 from the viewpoint of promoting the reduction of the viscosity of the pigment dispersion. , 500 to 3,000. If the number average molecular weight is 800 or more, sufficient steric repulsion can be generated to improve the dispersibility, and if it is 4,000 or less, it is suitable for lowering the viscosity of the pigment dispersion.
The number average molecular weight of the alkyl (meth) acrylate macromer should be measured using polystyrene as a standard substance by gel chromatography (GPC) method using chloroform containing 1 mmol / L lauryldimethylamine as a solvent. Can

[Particularly preferred specific examples of the polymer dispersant]
Specific examples of the polymer dispersant of the present invention include graft polymers having the following main chain and side chain.
Main chain: a structural unit (a ′) derived from N-vinyl-2-pyrrolidone and a structural unit (b) derived from a vinyl monomer containing a hydroxyl group, the structural unit (a) in the polymer dispersant Is 2 to 30% by weight, and the structural unit (b) is 5 to 30% by weight.
Side chain: contains a structural unit (c) derived from an alkyl (meth) acrylate macromer having a number average molecular weight of 800 to 4,000, and the content of the structural unit (c) in the polymer dispersant is 65 to 5,000. 92% by weight.
The content of the structural unit (a) or (a ′), (b) and (c) in the polymer dispersant is the same as that of the structural unit (a) or (a ′), ( This corresponds to the charged amount of monomer corresponding to each of b) and (c).

(Production of polymer dispersant)
The above particularly preferred polymer dispersant is composed of a monomer mixture containing N-vinyl-2-pyrrolidone, a vinyl monomer containing a hydroxyl group, and an alkyl (meth) acrylate macromer (hereinafter referred to as “monomer mixture”). It can be obtained by polymerization. The monomer mixture may further contain an alkyl (meth) acrylate or the like within a range not impairing the object of the present invention.
The content of N-vinyl-2-pyrrolidone in the monomer mixture is 2 to 30% by weight, preferably 5 to 25% by weight, from the viewpoint of dispersion stability of the organic pigment in the pigment dispersion. Preferably it is 10 to 20% by weight.
From the viewpoint of dispersion stability of the organic pigment in the pigment dispersion, the content of the hydroxyl group-containing monomer in the monomer mixture is 5 to 30% by weight, preferably 5 to 25% by weight, more preferably 10 to 10%. 20% by weight.
The content of the alkyl (meth) acrylate macromer in the monomer mixture is 65 to 92% by weight, preferably 65 to 85% by weight, from the viewpoint of improving the dispersion stability of the organic pigment in the pigment dispersion. More preferably, it is 65 to 80% by weight.

The polymer dispersant can be produced by copolymerizing the monomer mixture by a known polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method. Among these polymerization methods, the solution polymerization method is preferable from the viewpoint of using an organic solvent for the pigment dispersion.
As the organic solvent used in the solution polymerization method, an organic solvent having a high affinity with the graft polymer is preferable, and the above organic solvents can be used.
In the polymerization, azo compounds such as 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), tert-butyl peroxyoctoate, dibenzoyl peroxide, etc. Known radical polymerization initiators such as organic peroxides can be used.
The amount of the radical polymerization initiator is preferably 0.001 to 5 mol, more preferably 0.01 to 2 mol, per mol of the monomer mixture.
In the polymerization, a known polymerization chain transfer agent such as mercaptans such as octyl mercaptan and 2-mercaptoethanol and thiuram disulfide can be further added.
Although the polymerization conditions of the monomer mixture vary depending on the type of polymerization initiator, monomer, and organic solvent used, the polymerization temperature is usually 30 to 100 ° C., preferably 50 to 80 ° C., and the polymerization time is the polymerization temperature, etc. However, it is usually about 1 to 20 hours. The polymerization atmosphere is preferably an inert gas atmosphere such as nitrogen gas or argon.
After completion of the polymerization reaction, the produced polymer can be isolated from the reaction solution by a known method such as reprecipitation or solvent distillation. Further, the obtained polymer can be purified by repeating reprecipitation or by removing unreacted monomers and the like by membrane separation, chromatography, extraction and the like.

  The weight average molecular weight (Mw) of the obtained polymer dispersant is preferably 5,000 to 200,000 from the viewpoint of improving the dispersion stability of the organic pigment in the pigment dispersion, particularly the diketopyrrolopyrrole pigment. 5,000 to 100,000 are more preferable, and 6,000 to 70,000 are particularly preferable. In addition, the weight average molecular weight of a polymer is measured using polystyrene as a standard substance by gel chromatography (GPC) method using chloroform containing 1 mmol / L lauryldimethylamine as a solvent.

[Composition of pigment dispersion]
The amount of the pigment in the pigment dispersion is preferably 1% by weight or more, more preferably 5% by weight or more, and still more preferably 10% by weight or more from the viewpoint of improving productivity during dispersion. Further, from the viewpoint of ensuring handling properties at the time of dispersion, it is preferably 60% by weight or less, more preferably 50% by weight or less, and still more preferably 40% by weight or less.
The amount of the solvent in the pigment dispersion is the amount excluding the pigment concentration, polymer dispersant, and other additives, and is 30% by weight or more, preferably 50% by weight or more from the viewpoint of improving the operability during the dispersion treatment. More preferably, it is 70% by weight or more.
The amount of the polymer dispersant in the pigment dispersion is preferably an addition amount that does not become deficient in the dispersion treatment process from the viewpoint of improving the dispersion stability. Specifically, it is 5% by weight or more, preferably 7% by weight or more, more preferably 10% by weight or more based on the pigment weight. Further, from the viewpoint of obtaining an appropriate viscosity of the dispersion, it is 200% by weight or less, preferably 100% by weight or less, and more preferably 80% by weight or less based on the pigment weight.

<Production of non-aqueous pigment dispersion>
In the method for producing a non-aqueous pigment dispersion of the present invention, the following steps (1) and (2) are performed.
Step (1): Step of obtaining a pigment dispersion by mixing a pigment, an organic solvent, and a polymer dispersant Step (2): An alcohol having 1 to 5 carbon atoms is added to the pigment dispersion obtained in Step (1). After removing the polymer, filtering process to remove the polymer dispersant

[Step (1)]
Step (1) is a step of obtaining a pigment dispersion by subjecting a mixture (hereinafter simply referred to as “mixture”) obtained by mixing a pigment, an organic solvent, and a polymer dispersant to dispersion treatment.
Although there is no particular limitation on the mixing order of each component, it is possible to add a pigment to an organic solvent from the viewpoint of enhancing productivity in consideration of the bulk specific gravity of the pigment and the ease of mixing the pigment and the organic solvent. preferable. The polymer dispersant is preferably added before or after the pigment is added.
The mixture can be atomized only by the main dispersion until the average particle size reaches the desired particle size, but preferably after pre-dispersion, the mixture is further dispersed by applying shear stress to obtain the desired average particle size. It is preferable to control so that it may become the particle size of this.

(Preliminary dispersion)
As a mixing device used for predispersing the mixture, a commonly used mixing and stirring device such as an anchor blade can be used. Among the mixing and stirring devices, Ultra Disper (Iwata Iron Works Co., Ltd., trade name), Ebara Milder (Ebara Manufacturing Co., Ltd., trade name), TK homomixer, TK pipeline mixer, TK homojetter, TK homomic line flow, Philmix (above, Primix Co., Ltd., trade name), Ultra Turrax, DISPAX-REACTOR, Colloid Mill, CMS, MHD (IKA Japan Co., Ltd., trade name), Clear Mix (M Technique Co., Ltd., trade name), A high-speed stirring and mixing apparatus such as KD Mill (Kinetic Dispersion, trade name) is preferred.
When the mixture is predispersed, two or more predispersion treatments or different predispersion treatments may be combined from the viewpoint of reducing the content of coarse particles after the step (1). The number of preliminary dispersion treatments is preferably 10 times or less, more preferably 5 times or less, from the viewpoint of complexity and productivity.
For example, it is preferable to adjust the average particle size (50% passing particle size in the volume average particle size distribution: D50) of the pigment after preliminary dispersion to 0.2 μm or less, preferably 0.15 μm or less. Further, from the viewpoint of reducing the content of coarse particles, D90 after pre-dispersion (90% passing particle diameter in volume average particle size distribution) is preferably 1 μm or less, more preferably 0.6 μm or less, It is particularly preferable that the thickness be 0.4 μm or less. The average particle size (D50) and D90 can be measured by a dynamic light scattering particle size distribution meter or a laser Doppler particle size distribution meter that can measure the particle size range.

(Distributed)
Examples of the mixing apparatus used for the dispersion include a kneader such as a roll mill, a kneader, and an extruder, a star mill (Ashizawa Finetech Co., Ltd., trade name), an ultra apex mill (Koto Kogyo Co., Ltd., trade name), and a pico mill (Soda). Iron Works Co., Ltd. (trade name), DCP Super Flow, Cosmo (Japan Eirich Co., Ltd., trade name), MSC mill (Mitsui Mining Co., Ltd., trade name) and other bead mills, high-pressure homogenizer [Izumi Food Machinery Co., Ltd., trade name] , Homovalve type high-pressure homogenizer represented by Minilab 8.3H (Rannie, trade name), Microfluidizer (Microfluidics, trade name), Nanomizer (Nanomizer, trade name), Ultimateizer (Sugino Machine Co., Ltd.) , Product name], Genus PY (Shiramizu Chemical Co., Ltd., product) ), DeBEE2000 (Japan Biii Co., Ltd., and trade name) chamber type high-pressure homogenizer or the like of such.
In addition, from the viewpoint of reducing the content of coarse particles after the step (1), two or more main dispersion processes or different main dispersion processes may be combined.
Among these, a bead mill is preferable as the present dispersion device from the viewpoint of reducing the particle size of the pigment contained in the mixture.

[Step (2)]
Step (2) is a step of adding a C1-5 alcohol to the pigment dispersion obtained in step (1), followed by filtration to remove the polymer dispersant. By this filtration treatment, the content of the polymer dispersant not adsorbed on the unstable pigment generated in step (1) is reduced, the polymer dispersant adsorbed excessively on the pigment is removed, and the pigment dispersion is removed. Can be purified.
(C1-C5 alcohol)
The alcohol having 1 to 5 carbon atoms is preferably a saturated monohydric alcohol having 1 to 5 carbon atoms, such as methanol, ethanol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, s-butyl alcohol, t-butyl alcohol, Examples include various pentyl alcohols. Among these, a saturated monohydric alcohol having 2 or 3 carbon atoms is preferable, and ethanol is particularly preferable. The addition amount of the alcohol having 1 to 5 carbon atoms is preferably 10 to 1000 parts, more preferably 30 to 500 parts, with respect to 100 parts of the pigment dispersion.

(Filtration treatment)
Although there is no restriction | limiting in particular in the method of filtration treatment, Ultrafiltration treatment and / or microfiltration treatment are preferable. There is no particular limitation on the filtration method, and either a full-volume filtration method or a cross-flow filtration method may be used, but from the viewpoint of preventing the suspended substances in the supplied dispersion from depositing on the membrane surface, the Cruz flow filtration method. Is preferred. As the pore diameter of the filtration membrane to be used, pore diameter regions such as a microfiltration membrane (MF membrane) and an ultrafiltration membrane (UF membrane) can be used. The pore diameter of the filtration membrane is preferably 1 to 50 nm, more preferably 2 to 30 nm, and still more preferably 3 to 20 nm.
The filtration membrane used is not particularly limited as long as it does not deteriorate with an organic solvent. For example, cellulose film, 304 and 316 stainless steel film, bleached cotton film, polysulfone (PS) film, polypropylene (PP) film, polyethersulfone (PES) film, polyethylene terephthalate (PET) film, polyvinylidene fluoride (PVDF) Examples thereof include filtration membranes mainly composed of various materials such as a membrane, a polycarbonate (PCTE) membrane, and polytetrafluoroethylene (PTFE). Among these, a polysulfone (PS) film, a polytetrafluoroethylene (PTFE) film, a polyethersulfone (PES) film, a polyethylene terephthalate (PET) film, a polyvinylidene fluoride film, and a polycarbonate (PCTE) film are preferable. Ether sulfone (PES) membranes are more preferred.

  Examples of the filtration membrane used for microfiltration include a depth type (thickness filtration type) that traps foreign matters inside the filter medium, and a surface type (surface filtration type) that traps foreign substances on the surface of the filter medium. Commercially available filtration membranes used for microfiltration include surface-type 304 stainless steel such as Nippon Shokubai's Epocell, Nihon Pole Co., Ltd.'s Pole Cell, etc., Nihon Pole Co., Ltd.'s Rigimesh. Membranes, polypropylene membranes such as micro pure manufactured by Loki Techno Co., 316 stainless steel membranes such as Sus Pure manufactured by Loki Techno Co., and polypropylene membranes such as TCP, TCPE, TC manufactured by Toyo Filter Paper Co., Ltd. For depth types, profiles manufactured by Nippon Pole Co., Ltd., micro-Syria, Dia, Dia II (P), Dia II (C), Pureron, Syria Clean, SL, SLN, Glaslon, Toyo Filter Paper, manufactured by Loki Techno Co., Ltd. Examples thereof include polypropylene films such as TCPD, TCW-PP, TCW-CS, and TCW-EP manufactured by Corporation.

Although ultrafiltration is performed under pressure or reduced pressure, examples of commercially available filtration membranes include NTU series product names manufactured by Nitto Denko Corporation: 2020, 2120, 3520, 3150, 3006, 3050, 3250, 3550, 4208, 4220, trade names of NFS series: 100, 101, 103, polysulfone membranes such as NTM-9002, RS-30, AIP-0013, ACP-0013, ACP-0053, manufactured by Asahi Kasei Corporation Product name of AHP-0013, AIV series: 3010, 5010, Product name of ACV series: 3010, 3050, 5010, 5050, SIW-3054, SEP-0013, SAP-0013, SIP-0013, SLP-0053, Microza Polyvinylidene fluoride membrane, etc., Toyobo Co., Ltd. Mini cross, and polypropylene films, such as cross-flow module.
Examples of the shape of the membrane include a hollow fiber type, a tube type, a flat plate type, a monolith type, and the like, and the method of flowing the dispersion may be an internal pressure filtration method or an external pressure filtration method.
Moreover, as an ultrafiltration apparatus which has an ultrafiltration membrane, a commercially available thing can be used, For example, Centriprep made from Amicon, Pericon, Millitan, etc. made from Millipore are mentioned for research.
Among the above, a crus flow filtration method using an ultrafiltration membrane is more preferable. Further, a diafiltration method that performs filtration while adding an organic solvent is also preferable.

In the present invention, the polymer dispersant not adsorbed on the pigment is removed by filtration treatment, but from the viewpoint of enhancing the storage stability, the polymer dispersant not adsorbed on the pigment in the dispersion after the filtration treatment The concentration of is preferably 1.8% by weight or less, more preferably 1.5% by weight or less, and still more preferably 1% by weight or less, and it is further preferred that no unadsorbed polymer is present. The lower limit is not particularly limited, but is preferably 0.01% by weight or more from the viewpoint of productivity and storage stability.
Furthermore, the amount of the polymer dispersant adsorbed on the pigment is preferably 60% by weight or less, more preferably 55% by weight or less, and still more preferably 50% by weight or less, from the viewpoint of storage stability of the pigment dispersion. is there. The amount of the polymer dispersant adsorbed on the pigment can be measured by the method described in the examples.

<Coloring composition for color filter>
Since the non-aqueous pigment dispersion obtained by the production method of the present invention is excellent in storage stability, it is particularly useful as a coloring composition for a color filter produced by an ink jet method. That is, it can be used as a color filter coloring composition (color resist coloring material) by adding and mixing various binders, polyfunctional monomers, photopolymerization initiators, solvents, additives and the like.
Examples of the polyfunctional monomer include (meth) acrylic acid ester, urethane (meth) acrylate, (meth) acrylic acid amide, allyl compound, and vinyl ester having two or more ethylenically unsaturated double bonds. The content of the polyfunctional monomer is preferably 10 to 60% by weight with respect to the total solid content in the pigment dispersion composition.
Examples of the photopolymerization initiator include aromatic ketones, lophine dimers, benzoin, benzoin ethers, and polyhalogens. In particular, a combination of 4,4′-bis (diethylamino) benzophenone and 2- (o-chlorophenyl) -4,5-diphenylimidazole dimer, 4- [pN, N-di (ethoxycarbonylmethyl) -2, 6-di (trichloromethyl) -s-triazine] is preferred. A photoinitiator can be used individually or in combination of 2 or more types. The content of the photopolymerization initiator is preferably 0.2 to 10% by weight with respect to the total solid content in the pigment dispersion composition.

In the following production examples, examples and comparative examples, “parts” and “%” are “parts by weight” and “% by weight” unless otherwise specified.
Measurement of the amount of the polymer dispersant remaining in the pigment dispersions obtained in Examples and Comparative Examples and evaluation of storage stability were performed by the following methods.
(1) Measurement of remaining amount of polymer dispersant The amount of remaining polymer dispersant after filtration is determined by measuring the amount of solids in the filtrate, that is, the amount of polymer dispersant, and the amount of polymer dispersant used for dispersion. It was calculated from the difference.
The amount of solid content in the filtrate can be measured from the weight after precisely weighing 1 g of the filtrate in an aluminum cup and dried in a 105 ° C. vacuum dryer (pressure 8 kPa) for 4 hours, and is obtained from the following formula (1). It is done.
Solid content (% by weight) in the supernatant liquid = [(total weight after drying−aluminum cup weight) / (total weight before drying−aluminum cup weight)] × 100 (1)

(2) Evaluation of storage stability The viscosity immediately after preparation of the pigment dispersion (before storage) was measured using an E-type viscometer [measurement temperature: 20 ° C., measurement time: 1 minute, rotation speed: 20 rpm, standard rotor (1 ° 34 ′ × R24)]. Similarly, the viscosity of the pigment dispersion after storage at 40 ° C. for 1 week is measured, the change in viscosity before and after storage is compared, the rate of increase in viscosity is calculated by the following formula (2), and the storage stability is evaluated. it can.
Viscosity increase rate = (viscosity after storage for 1 week at 40 ° C./viscosity immediately after preparation) × 100 (2)

Production Example 1 (Production of polymer dispersant)
Weigh 50 parts of methyl methacrylate, 25 parts of propylene glycol monomethyl ether acetate (PGMEA, organic solvent) and 5 parts of 3-mercaptopropionic acid (chain transfer agent) into a reaction vessel equipped with a nitrogen inlet tube, and seal with nitrogen. The temperature was raised to 75 ° C. Next, a mixture of 200 parts of methyl methacrylate, 100 parts of PGMEA, 16.7 parts of the chain transfer agent, and 2 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) (polymerization initiator) was added dropwise over 3 hours. did. Thereafter, a mixture of 125 parts of PGMEA, 0.9 part of the chain transfer agent, and 2 parts of the polymerization initiator was added dropwise over 1 hour, and further aged for 2 hours to obtain a number average molecular weight of 2,080 and a weight average molecular weight of 3,350. A methyl methacrylate macromer precursor was synthesized.
Subsequently, the nitrogen introduction tube was switched to an air introduction tube, and air was blown into the obtained macromer precursor with a gas pump, 23.3 parts of glycidyl methacrylate, 7.9 parts of tetrabutylammonium bromide, 0.8 parts of p-methoxyphenol Then, 17 parts of PGMEA was added and reacted at 90 ° C. for 10 hours to obtain a methyl methacrylate macromer having a number average molecular weight of 2,200, a weight average molecular weight of 3,500, and a solid content (effective content) of 60%.

In a reaction vessel equipped with a nitrogen introduction tube, 10 parts of PGMEA was measured, and the temperature was raised to 80 ° C. while sealing with nitrogen. 72.5 parts of methyl methacrylate macromer obtained in this reaction vessel as a solid content, 12.8 parts of N-vinyl-2-pyrrolidone, 14.7 parts of 2-hydroxyethyl methacrylate, 230 parts of a mixture of 120 parts of PGMEA, 2 parts of the polymerization initiator and 0.4 part of 2-mercaptoethanol (chain transfer agent) are added dropwise over 2 hours, and after the completion of the addition, the reaction is further performed for 3 hours to obtain a solid content (effective content) of 40%. A graft polymer (polymer dispersant) solution was obtained.
The obtained polymer was measured by gel chromatography (GPC) method using polystyrene as a standard substance. As a result, the number average molecular weight (Mn) was 5,200, and the weight average molecular weight (Mw) was 28,000.

Example 1
(1) Production of pigment dispersion mixture 75 parts of propylene glycol monomethyl ether acetate (PGMEA, SP value 8.73, boiling point 145 ° C.), polymer dispersant obtained in Production Example 1 (solid content 40%) A mixture of 5 parts was mixed with a homomixer (Primics Co., Ltd., trade name: Robomix) with stirring at 6,000 rpm, and a diketopyrrolopyrrole pigment (Ciba Specialty Chemicals Co., Ltd., C.I) as a pigment. Pigment Red 254, trade name “Irgaphor Red BT-CF”, average primary particle size 30 nm (catalog value) 12.5 parts were added and stirred and mixed for 60 minutes to obtain a pigment dispersion mixture.
(2) Production of Preliminary Dispersion Dino Mill (manufactured by Shinmaru Enterprises, trade name, model 0.6L-ECM) in which the obtained pigment dispersion mixture was filled with 0.2 mmφ zirconia beads (filling rate 60% by volume) ) Was subjected to three passes in a continuous manner under the conditions of a stirring peripheral speed of 8 m / s and a residence time of 5 minutes to obtain a preliminary dispersion.
(3) Production of Pigment Dispersion Ultra Apex Mill (inner volume 0.17 L, manufactured by Kotobuki Industries Co., Ltd.), media type, in which the obtained preliminary dispersion was filled with 0.05 mmφ zirconia beads (filling rate 64 vol%) Disperser, trade name, model UAM-10, media particles: zirconia beads, particle size: 0.05 mm) were processed for 200 passes in a continuous mode under conditions of stirring peripheral speed 8 m / s and residence time 1.8 minutes. A pigment dispersion was obtained.
(4) Production of Pigment Dispersion A pigment dispersion obtained by diluting 100 parts of the pigment dispersion obtained in (3) above with 145 parts of PGMEA and further adding 13 parts of ethanol was obtained as an ultrafiltration membrane device (Millipore Corporation, Cross flow filtration by diafiltration method that continuously drops PGMEA at the same flow rate as permeation flow rate using Pellicon II cassette system, Biomax, V screen, PES membrane, fractional molecular weight 500kD, membrane area 0.1m ² ) While purifying, the total amount of the permeate was 1680 parts. During this time, in order to measure the amount of the removed dispersant, the permeate was sampled sequentially from the permeate side.
The amount of the polymeric dispersant remaining in the obtained pigment dispersion (ratio to the pigment in the pigment dispersion) was 55%. The results are shown in Table 1.

Comparative Example 1
A pigment dispersion obtained by diluting 100 parts of the pigment dispersion (3) obtained in Example 1 with 145 parts of PGMEA was treated in the same manner as in Example 1 using the ultrafiltration membrane device.
The amount of the polymer dispersant remaining in the obtained pigment dispersion (ratio to the pigment in the pigment dispersion) was 65%. The results are shown in Table 1.

  From Table 1, the pigment dispersion of Example 1 has a small viscosity immediately after filtration because the residual amount of the polymer dispersant remaining after filtration is small compared to the pigment dispersion of Comparative Example 1, and after storage. It can be seen that the viscosity increase rate is small, that is, the storage stability is improved.

Claims (6)

  After adding an alcohol having 1 to 5 carbon atoms to a pigment dispersion obtained by mixing a pigment, an organic solvent, and a water-insoluble polymer dispersant, the water-insoluble polymer dispersant is removed by filtration. A method for producing a non-aqueous pigment dispersion.   The method for producing a non-aqueous pigment dispersion according to claim 1, wherein the alcohol is ethanol.   The method for producing a non-aqueous pigment dispersion according to claim 1 or 2, wherein the filtration treatment is ultrafiltration treatment and / or microfiltration.   The manufacturing method of the non-aqueous pigment dispersion in any one of Claims 1-3 whose filtration process is a crossflow filtration process.   The manufacturing method of the non-aqueous pigment dispersion in any one of Claims 1-4 whose filtration process is a diafiltration process.   The coloring composition for color filters containing the non-aqueous pigment dispersion obtained by the method in any one of Claims 1-5.